I. Field of the Invention
The present invention relates to artificial molar teeth capable of easy arrangement when making a dental prosthetic appliance, and easy chewing at the time of mounting it as dentures.
II. Description of Related Art
Arrangement of artificial molar teeth when making a dental prosthetic appliance demands advanced techniques and experience. It has been particularly difficult to arrange opposed teeth in a proper position relative to each other. In conventional artificial teeth, the relation of cusps and fossae of the teeth has been considered to be important, and it has been desirable to make a stable shape so that it is possible for each of a plurality of cusps to engage with the fossae. Further, it has been desirable to develop artificial teeth which do not require much grinding after arrangement or large changing of the surface state.
Japanese Patent Application Laid-Open No. 2002-177301 discloses artificial molar teeth in which a lingual cusp, a buccal cusp, and a fossa are formed on the occlusal surface of maxillary molar teeth, and also a lingual cusp, a buccal cusp, and a fossa are formed on the occlusal surface of antagonist, i.e. opposed mandibular molar teeth. These artificial molar teeth are configured such that at a central occlusal position the lingual cusp of the maxillary molar teeth occludes and contacts with the fossa of the mandibular antagonist, and the buccal cusp of the mandibular antagonist occludes and contacts with the fossa of the maxillary molar teeth.
In the artificial molar teeth disclosed in Japanese Patent Application Laid-Open No. 2002-177301, occlusal contact occurs in a total of 18 points, 9 points at the left and 9 points at the right. In other words, the number of occlusal contact points is smaller than in the full-balanced occlusion, and there is no occlusal contact with the inclined surface of the buccal cusp as in the full-balanced occlusion. Accordingly, when making dentures, arrangement on the wax alveolar ridge or occlusal adjustment by grinding or the like is easy. When the dentures are used, the dentures are stable without falling over. In mastication efficiency including grinding, biting and cutting of food, a satisfactory occlusion close to the full-balanced occlusion will be obtained. Moreover, changing to a lingualized occlusion can be easily conducted not only when making dentures but also when correcting the dentures.
However, in the artificial molar teeth disclosed in Japanese Patent Application Laid-Open No. 2002-177301, it is required to achieve occlusal contacts between the lingual cusp of maxillary molar teeth and the fossa of mandibular antagonist, and between the fossa of maxillary molar teeth and the buccal cusp of mandibular antagonist, respectively. Therefore, it has been extremely difficult to make dentures for each patient according to the complicated oral cavity environments of patients. Besides, the cusp of the artificial molar teeth may be distorted in a molding process. Therefore, it is extremely difficult to mold the cusp in a shape exactly engaging with the fossae of the antagonist, causing the disadvantage of poor yield ratio.
Japanese Patent Application Laid-Open No. 2006-42954 discloses an occlusion adjusting method in which cavities of a specified depth are provided on the occlusal surface of mandibular artificial teeth configuring dentures, and the cavities are filled with a plastic dental material of resin or an inlay wax of casing.
In Japanese Patent Application Laid-Open No. 2006-42954, in a state where the upper and lower dentures are occluded, by moving the lower jaw to the moving limits from front to back and side to side, the track of the lingual cuspal tops of the maxillary molar teeth contacting and passing on the occlusal surface of the mandibular molar teeth is recorded as a sliding and contacting trace on the surface of the plastic dental material or the inlay wax. By grinding this sliding and contacting trace according to a common dental method, the state of occlusion can be adjusted.
However, in the artificial molar teeth of Japanese Patent Application Laid-Open No. 2006-42954, the cuspal portion of the occlusal surface side and the tooth root portion of the root side need to be formed in different molds, and it is necessary to adjust occlusion by taking the motion of jaw in an oral cavity. Therefore, the making process of the dentures is long and complicated, and the burden to a patient was significant.